1. Field of the Invention
This invention relates to the construction and manufacture of cartridge fuses and in particular to a cartridge fuse having interally formed knife-blade ferrule terminals.
2. Description of the Prior Art
The prior art discloses a variety of cartridge fuses having knife-blade ferrule terminals. In the typical fuse of this type, a knife-blade ferrule terminal is secured to each end of a hollow tube of insulating material encasing a fusible strip connected between the ferrule terminals. The ferrule terminals, which may be of a one or two piece construction, each include a ferrule portion sized to fit over its respective end of the insulating tube, and a knife-blade terminal portion which is adapted to be secured in a conventional knife-blade fuse holder. Regardless of whether the ferrule terminal is of a one or two piece construction, when assembling fuses of this type it has generally been fairly difficult to properly align and secure the fusible strip to the ferrule terminals. For example, in fuses where the fusible strip is soldered to the ferrule terminals, the amount and distribution of the solder on the terminal can significantly affect the integrity of the bond between the fusible strip and the terminals. Too little or improperly placed solder can result in a defective electrical connection between the fusible strip and the terminals, and too much solder can result in excessive heat dissipation which adversely affects the short circuit performance of the fuse. This soldering operation is particularly difficult since it must be accomplished in a blind manner while the ferrule terminals are being assembled on the tube forming the body of the fuse. In addition to the foregoing, ferrule terminals of a two piece construction are inherently susceptable to the chance of a defective bond between the parts of the ferrule terminal as well as the usual manufacturing problems associated with insuring the concentricity of the ferrule and terminal portions of the terminal. This is of particular concern in fuses of this type since proper alignemnt of the fuse in its respective fuse holder is generally essential to obtain an adequate electrical connection between the knife-blade terminals and the fuse holder.